Add platform support documentation for x86_64h-apple-darwin

src/doc/rustc/src/SUMMARY.md

@@ -40,6 +40,7 @@
     - [wasm64-unknown-unknown](platform-support/wasm64-unknown-unknown.md)
     - [x86_64-fortanix-unknown-sgx](platform-support/x86_64-fortanix-unknown-sgx.md)
     - [x86_64-unknown-none](platform-support/x86_64-unknown-none.md)
+    - [x86_64h-apple-darwin](platform-support/x86_64h-apple-darwin.md)
 - [Targets](targets/index.md)
     - [Built-in Targets](targets/built-in.md)
     - [Custom Targets](targets/custom.md)

src/doc/rustc/src/platform-support.md

@@ -322,5 +322,6 @@ target | std | host | notes
 `x86_64-uwp-windows-gnu` | ✓ |  |
 `x86_64-uwp-windows-msvc` | ✓ |  |
 `x86_64-wrs-vxworks` | ? |  |
+`x86_64h-apple-darwin` | ✓ | ✓ | macOS with late-gen Intel (at least Haswell)
 
 [runs on NVIDIA GPUs]: https://github.com/japaric-archived/nvptx#targets

src/doc/rustc/src/platform-support/x86_64h-apple-darwin.md

@@ -0,0 +1,57 @@
+# `x86_64h-apple-darwin`
+
+**Tier: 3**
+
+Target for macOS on late-generation `x86_64` Apple chips, usable as the
+`x86_64h` entry in universal binaries, and equivalent to LLVM's
+`x86_64h-apple-macosx*` targets.
+
+## Target maintainers
+
+- Thom Chiovoloni `[email protected]` <https://github.com/thomcc>
+
+## Requirements
+
+This target is an `x86_64` target that only supports Apple's late-gen
+(Haswell-compatible) Intel chips. It enables a set of target features available
+on these chips (AVX2 and similar), and MachO binaries built with this target may
+be used as the `x86_64h` entry in universal binaries ("fat" MachO binaries), and
+will fail to load on machines that do not support this.
+
+It should support the full standard library (`std` and `alloc` either with
+default or user-defined allocators). This target is probably most useful when
+targetted via cross-compilation (including from `x86_64-apple-darwin`), but if
+built manually, the host tools work.
+
+It is similar to `x86_64-apple-darwin` in nearly all respects, although the
+minimum supported OS version is slightly higher (it requires 10.8 rather than
+`x86_64-apple-darwin`'s 10.7).
+
+## Building the target
+
+Users on Apple targets can build this by adding it to the `target` list in
+`config.toml`, or with `-Zbuild-std`.
+
+## Building Rust programs
+
+Rust does not yet ship pre-compiled artifacts for this target. To compile for
+this target, you will either need to build Rust with the target enabled (see
+"Building the target" above), or build your own copy of `core` by using
+`build-std` or similar.
+
+## Testing
+
+Code built with this target can be run on the set of Intel macOS machines that
+support running `x86_64h` binaries (relatively recent Intel macs). The Rust test
+suite seems to work.
+
+## Cross-compilation toolchains and C code
+
+Cross-compilation to this target from Apple hosts should generally work without
+much configuration, so long as XCode and the CommandLineTools are installed.
+Targetting it from non-Apple hosts is difficult, but no moreso than targetting
+`x86_64-apple-darwin`.
+
+When compiling C code for this target, either the "`x86_64h-apple-macosx*`" LLVM
+targets should be used, or an argument like `-arch x86_64h` should be passed to
+the C compiler.